On April 3, 1984, a private physician reported four cases of
trichinosis among Laotians living in Amarillo, Texas, to the Bureau
of
Epidemiology, Texas Department of Health. The four patients were
members of three households and had onset of illness between
February
21 and March 12. Because of the large Laotian population resettled
in
this area and its previously noted practice of inadequately cooking
pork (1), an investigation was begun to determine the extent of the
outbreak. A survey, seeking a history of symptoms commonly seen
with
trichinosis (fever, muscle pain, periorbital edema, and malaise),
was
undertaken in households of known patients and their Laotian
neighbors. If symptoms of trichinosis were present, serum was
obtained for serodiagnosis.

During the investigation, five additional cases of trichinosis
were found. Three persons with possible trichinosis were also
identified but had moved to California to an unknown address and
could
not be contacted. All nine patients were Laotian, living in four
unrelated households. All reported consuming pork purchased at a
small local pig farm. Incubation periods for six patients ranged
from
4 days to 2 weeks; for three who frequently consumed pork from the
implicated farm, they were indeterminable. All patients were
asymptomatic when interviewed but reported having the following
symptoms: fever (all nine persons (100%)), muscle pain (six
(67%)),
malaise (six (67%)), periorbital edema (five (56%)), vomiting (two
(22%)), and diarrhea (two (22%)). One person was pregnant.
Laboratory studies of those seen by a physician during acute
illness
revealed eosinophilia and elevated creatine kinase. Five of the
six
patients tested for antibody to Trichinella sp. with the bentonite
flocculation test had titers of 1:10 or greater, compatible with
recent infection, and the remaining patient had a titer of 1:5. No
patients had previous serologic testing to demonstrate
seroconversion. A muscle biopsy performed on one patient was
negative
for Trichinella sp. but had areas of slight basophilic degenerative
changes with focal eosinophilic infiltration. Of the five patients
treated during acute disease, three received prednisone and
thiabendazole; one, prednisone only; and one, thiabendazole only.
The
patient treated with thiabendazole developed pruritis after 2 days
of
therapy, but it disappeared when the drug was discontinued.

Investigation by the Texas Department of Health revealed that
the
pigs on the farm were occasionally fed untreated restaurant refuse;
in
addition, the animals wandered freely, allowing potential contact
with
rodent and other animal carcasses. The Texas Animal Health
Commission
inspected the farm but saw no evidence that garbage was being fed
to
the pigs at the time. The farm had previously been implicated as
the
source of a Trichinella sp. infection in 1981.

No further cases have been reported. None of the patients
developed complications; the outcome of the pregnancy is unknown.
Serum from pigs at the implicated farm is being sent to the U.S.
Department of Agriculture to test for trichinosis antibody. In an
effort to educate the Laotian population, the Texas Department of
Health is developing a pamphlet on trichinosis and its prevention
written in Laotian.
Reported by C Reed, MPH, J Norred, H Moritz, MD, Public Health
Region
1, CE Alexander, MD, State Epidemiologist, Texas Dept of Health;
Div
of Parasitic Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Trichinella spiralis, first noted to be pathogenic
for humans in 1859 (2), remains a public health problem in the
United
States. Infection occurs when raw or inadequately cooked meat,
most
commonly pork, is ingested. Of cases reported during 1975-1981,
where
an infected meat item was identified, pork was implicated in 79.1%;
wild meat, in 13.9%; and ground beef, in 7.0%. The incriminated
ground beef was believed to have been adulterated by pork products
(3).

Commercially or privately slaughtered pigs are not inspected
for
trichinae in the United States (4). Nevertheless, the reported
incidence of trichinosis has declined in the United States from 300
to
400 cases annually in the late 1940s to about 100-150 cases per
year
(3). This can be attributed, in part, to: (1) state and federal
laws
that prohibit feeding untreated garbage to swine (5); (2) consumer
awareness of the need to cook pork products adequately; and (3) the
widespread practice of freezing pork, which kills trichinae (6).
An
estimated one million garbage-fed swine reach the market annually
(4);
law enforcement concerning feeding untreated garbage to swine
varies
from state to state. Moreover, it has been shown that swine
readily
feed on barnyard rodents that may harbor Trichinella sp. and may
thus
become infected (6). Consequently, trichinosis control depends
almost
entirely on the way consumers store and prepare pork.

Groups whose food preferences include raw or inadequately
cooked
pork have a higher risk of trichinosis (3). This is reflected in
the
ethnic-related prevalance of trichinosis. In an autopsy survey,
the
prevalence of infection among German and Italian immigrants in the
United States was nearly twice the national rate (28.3%, 29.7%, and
16.1%, respectively) (7). Recent reports of trichinosis outbreaks
(2)
involve groups, especially such recent immigrants as Southeast
Asian
refugees, who do not treat, freeze, or thoroughly cook American
pork.
To help prevent future outbreaks, special health-education programs
may be necessary for these new consumers.

Wright WH, Jacobs L, Walton AC. Studies on trichinosis. XVI.
Epidemiological considerations based on the examination for
trichinae of 5,313 diaphragms from 189 hospitals in 37 states
and
the District of Columbia. Public Health Rep 1944;59:669-81.

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